Advances in plasma processing have facilitated growth in the semiconductor industry. The semiconductor industry is a highly competitive market. The ability for a manufacturing company to be able to process substrates in different processing conditions may give the manufacturing company an edge over competitors. Thus, manufacturing companies have dedicated time and resources to identify methods and/or arrangements for improving substrate processing.
A typical processing system that may be employed to perform substrate processing may be a capacitively-coupled plasma (CCP) processing system. The plasma processing system may be built to enable processing in a range of process parameters. However, in recent years, the types of devices that may be processed have become more sophisticated and may require more precise process control. For example, devices being processed are becoming smaller with finer features and may require more precise control of plasma parameters, such as plasma density and uniformity across the substrate, for better yield. Pressure control of the wafer area in the etching chamber may be an example of a process parameter affecting plasma density and uniformity.
The manufacturing of semiconductor devices may require multi-step processes employing plasma within a plasma processing chamber. During plasma processing of semiconductor device(s), the plasma processing chamber may typically be maintained at a predefined pressure for each step of the process. The predefined pressure may be achieved through employing mechanical vacuum pump(s), turbo pump(s), confinement ring positioning and/or combinations thereof, as is well known by those skilled in the art.
Conventionally, a valve assembly may be employed to throttle the exhaust turbo pump(s) to attain pressure control for maintaining predefined pressure conditions in the plasma processing chamber. However, the pressure being controlled by the vat valve may result in a global change in the entire chamber without the capability of providing differential pressure control in different regions of the chamber.
In the prior art, the pressure in the plasma generating region of the plasma processing chamber (e.g., the region encapsulated by the two electrodes and surrounded by the confinement rings) may be controlled by adjusting the gaps between the confinement rings of a confinement ring assembly. Adjusting the gaps controls the flow rate of exhaust gas from the plasma generating region and pressure may be affected as a result. The overall gas flow conductance out of the plasma generating region may depend on several factors, including but not limited to, the number of confinement rings and the size of the gaps between the confinement rings. Thus, the operating windows for the pressure range may be limited by the chamber gap and/or the gaps of these confinement rings. Furthermore, the plasma cross section may be a fixed diameter for the aforementioned process due to the fix diameter of these confinement rings.
In the prior art, a plasma processing chamber configured with the capability to sustain a plurality of differentiated plasma volumes may be employed to address the aforementioned problem of plasma of fixed cross section. In an example, a wide-gap configuration may be employed to provide an increased plasma cross section with relatively low pressure. In another example, a narrow-gap configuration may be employed to provide the conventional plasma cross section but relatively higher pressure may be attained. However, active differentiated pressure control for the system is not provided.
In view of the need to process the substrate in multiple steps, each of which may involve a different pressure, improvement to the capability to provide differentiated pressure control over a wider range of pressure in plasma processing systems is highly desirable.